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Low-Dose ACTH (Cosyntropin) Stimulation Test

What is a low-dose ACTH (cosyntropin) stimulation test?

Illustration of the brain's stress response showing the hypothalamus, pituitary gland, adrenal gland, and cortisol

The adrenal glands lie above the kidneys and are part of the HPA axis. The hormone ACTH from the pituitary signals the adrenal glands to release the hormone cortisol. Cortisol controls important body functions. This is known as the stress response.

A low-dose ACTH (cosyntropin) test measures the function of the body’s HPA axis (hypothalamic-pituitary-adrenal axis). This system is made up of:

  • A part of the brain called the hypothalamus
  • The pituitary gland in the brain
  • The adrenal glands, located just above the kidney

The pituitary gland makes substances known as hormones. One of these hormones is called ACTH. ACTH signals the adrenal glands , to release another hormone called cortisol. Cortisol is released during stressful situations and controls body functions such as:

  • Balancing the levels of water and salts
  • Keeping blood pressure normal

Cortisol also helps the body use nutrients and respond to stress.

Doctors use the low-dose ACTH test to help diagnose a condition known as central adrenal insufficiency. They also use this test to check the pituitary gland’s function. The pituitary may not work correctly after treatment with radiation or steroids, or when a brain tumor is located near the pituitary.

For the low-dose ACTH test, the care team gives your child a low dose of a medicine called cosyntropin. It makes the adrenal glands release cortisol and other hormones into the blood. This test shows doctors how well your child’s hypothalamus and pituitary gland signal the adrenal glands to make cortisol.

How to prepare for the low-dose ACTH stimulation test

Your child can eat and drink as usual before the test. Give your child their usual medicine(s) on the morning of the test unless the care team tells you not to do so.

Testing lasts about 1 hour. Have your child wear comfortable clothes. Bring activities such as books, games, or tablets that they can do during the test.

If your child starts any new medicines, contact your health care provider before they have their test.

What to expect during the low-dose ACTH stimulation test

You can stay with your child during the test. Before the test, the care team will place an IV in your child’s arm.

  • The team will give cosyntropin through the IV.
  • The care team will draw blood samples through the IV for testing in the lab.
  • A nurse will check your child’s vital signs during the test.
  • At the end of the test, the nurse will remove the IV.

Possible side effects of the low-dose ACTH stimulation test

Your child should not have any side effects from the test.

After the low-dose ACTH stimulation test

Your child can return to normal activities after the test.

Key points about the low-dose ACTH stimulation test

  • A low-dose ACTH (cosyntropin) stimulation test is used to diagnose a condition known as central adrenal insufficiency and test pituitary function.
  • In this test, your child gets medicines that cause the adrenal glands to release hormones such as cortisol.
  • The nurse will take blood samples to measure the hormone released over time.
  • Your child should not have any side effects from the test and should be able to return to normal activities the same day.

Reviewed: August 2023